Thermostat



y ,1933 QAHANSER Em 1,916,671

THERMOSTAT Filed Juhe 16, 1930 mm mm whuzmk 1 q" ATTORNEY! Patented July4, 1933 UNITED STATES "PATENT OFFICE CHARLES A HANSER, 013 DETROIT, ANDERWIN A. LOCKWOOD, OF ROYAL OAK, MICHI- GAN, ASSIGNORS TO AMERICANELEUDBICAL HEATER COMPANY, OF DETROIT, MICHIGAN, A CORPORATION PFMICHIGAN rnnamosra'r L A Application filed June 16,

This invention relates to thermostats'and refers more particularly tothermostatic switch constructions for controlling electric vention is toprovide an improved thermostatic switch construction especially designedfor use in connection with electric irons wherein it is desirable tomaintain an approximate predetermined temperature without too frequentoperation of the circuit breaker.

The present invention contemplates the provision of a thermostat havingthermostatic elements responsive to variations in temperature togetherwith means for resisting operation of said elements upon slighttemperature changes to reduce the frequency of operation of theelements. The foregoing.

may be accomplished in several different ways as will be more fullyhereinafter set forth, especially when considered in connection with theaccompanying drawing,

wherein:

Figure 1 is an enlarged side elevational view of a thermostatic switchassembly constructed in accordance with this invention.

Figure 2 is a bottom Fi re 3 is a view similar to Figure 1 showing theparts in a different position.

t Figure 4 is a view similar to Figure 1 showing a slightly modifiedform of construction.

Figure 5 is a sectional View taken on the line 55 of Figure 4.

Figure 6 is a view similar to the above figures showing still anothermodified form of switch assembly.

Figure 7 is a sectional view taken on the line 7--7 of Figure 6.

Referring more in detail to the embodiment ofthe invention shown inFigure 1, it will be noted that there is illustrated in this fig; ure athermostatic switch assembly 10 comprising an attaching bracket 11having a de-' plan view of one of- 1930. Serial No. 461,534.

static strips 14 and 15 having the rear end portions thereof secured'tothe flange 13 by means of a single fastener element 16. As shown inFigure 1, the thermostatic strips 14 and 15 are supported in spacedrelation toeach other and to the flange 13 by the terminal members 17and 18 for respectively connecting the strips 14 and 15 in an electriccircuit. Both of the terminals 17 and 18 are secured in contactingrelation with the strips 14'and 15, respectively, by 'means of thefastener element 16, hereinbefore set forth, and are insulated frommetallic contact with each other and with the bracket by means ofsuitable insulating material designated generally by the referencecharacter 19.

. The thermostatic strips 14 and 15 are arranged in superposed relationand are provided with suitable contacts 20 and 21 adjacent the free endsthereof adapted to engage each other in the normal position of thestrips to close the electric circuit. The bithat upon a rise intemperature the free ends thereof move upwardly as a unit until theprojection 22 ezgtending upwardly from the lowermost strip engages theadjustable regulator designated generally by the reference character 23with the result that further upward movement of the lowermost strip 15is prevented.' Upon a continued rise in temperature, the upper strip 14continues to move upwardly with the result that the contacts 20 and 21are separated and'the electric circuit broken.

In order to effect a slight lag in the separation of the contacts 20 and21 to reduce the frequency of operation of the switch, we provide athird bimetallic thermostatic strip 24 disposed below the thermostaticstrip 14 with the outer end thereof secured to the free end of the strip14 as at 25 and the inner end thereof disposed above the contact 21 andadapted to carry the cooperating contact 20 hereinbefore set forth. Thearrangement is such that the current flowing through the strip 14-iscompelled to flow through the-third thermostatic strip 24 beforereachlng the contact '20. The strip 24 is so constructed thattemperature changes effect a movement metallic strips 14 and 15 are soconstructed 7 1y upon a rise in temperature.

thereof in directions opposite to the strip 14 set forth above. In otherwords,'a rise temperature causes the freeend of the strip 24 to movedownwardly or in. direction ,opposite the direction of movement of thefree end of the strip 14 with the result that when the temperature risesto cause an upward movement of the strips 14 and 15, the contacts 20 and21 are urged into more intimate engagement due to the tendency of thefree end of the strip 24 to move downwardly relative to the strip 14toward the strip 15.

With the construction as thus far described,

. it will be observed -that when the temperature surrounding thethermostat rises sufficient to cause upward movement of the strip 14relative to the strip 15 in the manner specified above, the contacts 20and 21 instead of separatingimm'ediately to break the current aremaintained in contacting relation due tothe fact that the strip- 24moves downwardnection it should be understood that the strip '24 issubstantially smaller in cross-sectional area than the strip. 14 andthereby oflers a greater resistance to theflow of current there throughwhich tends to'assist the surrounding temperature in heating the strip24 to a' greater degree than the latter strip 14 with the result thatthe strip 24 moves a greater distance than the strip 14 and therebyeffects a more intimate engagement of the contacts 20 and 21 upon arisein temperature. The

' strip 24 is also substantially shorter than the strip 14 so that uponan appreciable rise in temperature and upon continued upward movementofthe strip 14 to the position illustrated in Figure 3, the contacts 20and 21 are separated due to the inability of thestrip 24 to bridge thespace between the strip 14 and contact 21. a v

Assuming that the parts are in the position illustrated in Figure 3wherein the circuit is broken and no current is bein conducted throughthe strip 24, it will be 0 served that the temperature of the strip 24immediately falls and approaches the temperature of the strip 14 causingthe same to move upwardly toward the strip 14. As the surroundingtemperature falls, the strip 14 being of larger cross-sectional areathan the strip 24 moves the latter downwardly until the contacts 20 and21 come into engagement with each other to again close thecircuit- Theabove-construction is such as to prevent the contacts 20 and 21 fromcoming into' engagement with each other to close the circuit until thestrips 14 and 15' assume their lowermost' positions illustrated inFigure 1. Thus, from the foregoing it will be apparent that the'strip 24functions to resist separation and engagement of thecontacts withoutmaterially terfering with the movement of the thermostatlc strip 14 andalso that the lag in operat1on, effected by the strip 24, may be regu-In this conlated by varying the cross-sectional area of the strip 24 andthe length thereof.

Referring now to the embodiment of the invention illustrated inFiguresv4 and 5, it will be observed that the thermostatic switch shownin thesefigures is substantially the' ends of the thermostatic strips 30and 31, re-

spectively, and the upper thermostatic strip 30 is insulated as at 35from contact with the terminal member 36 with the result that thecurrent is prevented from flowing through the upper thermostatic stripbut, on the other hand. is conveyed to the contact 33 by means ofa'third bimetallic thermostatic strip, 37 a I having one end secured tothe terminal 36 to receive electrical energy therefrom and the oppositeend secured to the contact 33. The

third thermostatic strip 37 is constructed in i the same manner as thethermostatic strip 24,

set forth in connection with the first-described form of the invention,in that a rise in tem- Y perature tends to move the thermostatic strip37- downwardly and. a drop in temperature tends to move the, sameupwardly. The arrangement is such that movement of the uppermostthermostatic strip 30 under temperature variations is opposed by thethermostatic strip 37. The strip 37 is substantially smaller incross-sectional area than the strip 30 and offers an appreciableresistance to the passage of current therethrough with the result thatthe same is not only influenced by the surrounding temperature but alsoby the heat generated thereby. As a consequence, the'strip 37 isnormally at a greater temperature than the strip 30 and since, aspointed out above, the strip 37 is constructed to move downwardly upon arise in temperature, it

will be observed that thisstrip tends to move the contact 31into moreintimate engagement with the cooperating contact 34 upon a rise intemperature or, in other words, tends to resist upward movement of 'thethermostatic strip 30. Thethermostatic strip 30,

however, is considerably larger than the strip 37 with the result thatupon an appreciable rise in temperature the same will move upwardlyagainst the action of the strip 37 to break the contact between thepoints 33 and 34.

Assuming that the strip 30lis in its uppermost position wherein thecontact between the points'33 and 34,is broken, it will be ob-, servedthat since no current is flowing through the strip 37 the temperature ofthe latter will immediately fall and approach the temperature of thestrip 30 and owing to the fact that the strip ,37 is adapted to moveupwardly upon a drop in temperature, it will function to resist downwardmovement of the strip 30 for re-engaging the contacts 33 and 34. Thus,from the foregoing it Will be observed that the strip 37 resistsbothupward and down ward movement of the strip 30 and thereby eflects a lagin the operation of the switch.

The construction shown in Figures 6 and 7 differs from the arrangementjust described in, that the bimetallic thermostatic strip 40corresponding to the strip 37 in Figure 4 is interposed between a pairof bimetallic thermostatic strips 41 and 42 corresponding inconstruction to the strip 30 set forth above. As shown in Figure 6, thefree end of the thermostatic strip 40 extends beyond the thermostaticstrips 41'and 42 and carries a contact 43 for engagement with acooperating contact secured to the free end of the lowermostthermostatic strip 44. As shown in the construction illustrated inFigure 4, the electric energy in the present instance is transmitted tothe upper contact 43 through the thermostatic. strip 40 which, like-thestrips 24 and 37 hereinbefore described, is substantially small incross-sectional area to offer an appreciable resistance to the passageof current therethrough with the result that the temperature thereof isnormally higher than the temperature of the strips 41 and 42.

. The free end of the lowermost thermostatic strip 42 is normallyspaceda slight distance from the adjacent surface of the thermostaticstrip 40 with the result that upon an increase in temperature above apredetermined amount, the strip 42 moves upwardly into engagement withthe strip 40 tending to move the latter in the same direction. However,the strip 40 is constructed to move downwardly upon a rise intemperature and as a consequence tends to resist upward movement by thethermostatic strip 42. However, upon an appreciable rise in temperature,the strip 42 forces the strip 40 upwardly to break the contact betweenthe points 33 and 34. The function of the uppermost thermostatic strip41 is to return the strip 40 to the position shown in Figure 6 upon adrop in temperature, it being understood that as.

the temperature 'of the strip 40 lowers, the same tends to move upwardlyagainst the action of the thermostatic strip 41 thereby eflecting a lagin the operation of the switch.

While in describing the invention particular stress has been placed uponthe association of our improved meansas used in connection withthermostats having cooperating strip may be eliminated and the contactcar- I plished in numerous different ways and accordingly reservation ismade to make such changes as may'come within the purview of theaccompanying claims.

What we claim as our invention is: 1. A thermostat comprisingcooperating thermostatic elements movable laterally relativeto eachother under temperature changes,

and means for resisting relative movement of said elements.

2.-A thermostat comprising thermostatic elements movable laterallyrelative to each other under temperature changes, and temperatureresponsive means for resisting relative movement of said elements.

3. A thermostat comprising cooperating thermostatic elements movablelaterally relative to each other under temperature changes,

and another thermostatic element associated with the elements aforesaidand movable 1n opposite directions to the latter elements un-' inopposite directions to the elements aforesaid under temperature changesand operable to resist relative movement of said latter elements.

5. A thermostatic switch comprising thermostatic elements movablelaterally .under temperature changes, cooperating contacts movablerelative to each other by said elements for controllin the circuit tothe switch, and means or resisting relative movement of said contacts.

6. A thermostatic switch thermostatic. elements movable laterally undertemperature changes, cooperating contacts movable relative to each otherby said elements for making and breaking the circuit through the switch,and another thermostatic element movable in opposite directions to theelements aforesaid under temperature changes for resisting relativemovement of said contacts. J a

7. A thermostatic switch comprising thermostatic elements movablelaterally under temperature changes, cooperating contacts movablerelative to each other by said elements forjcontrolling the circuitthrough the switch, and another thermostatic element comprising operableby the first-mentioned elements and 9. A thermostatic switch comprisingthermostatic elements movable laterally relati-ve to each other undertemperature changes to control the circuit to the switch, andtemperature responsive means for efi'ecting a lag in the operation ofsaid thermostatic elements.

10. A thermostatic switch comprising thermostatic elements connected toa source of current and constructed to oppose each other undertemperature changes, and means operable at predetermined temperatures tocompel movement 'of said elements in the same direction.

11. A thermostatic switch comprising thermostatic elements connected toa source of current and constructed to oppose each other undertemperature changes cooperating contacts carried by the elements,another thermostatic element of substantially larger cross-sectionalarea than one of said firstmentioned elements and operable at apredetermined temperature to compel movement of the latter'in the samedirection as the cooperating element, and means for intercepting thelatter element permitting separation of said contacts. a

12. A thermostatic switch comprising a pair of freely separablecontacts, an arm resiliently urging one of said contacts in onedirection, a stop for limiting the movement of said arm, a secondcontactfa thermostatic strip operable to displace said secondcontact inthe same direction as said first contact upon rising temperatureconditions, a second thermostatic strip actin upon said second contactand'operable to isp lace said second contact in the opposite directionupon IlSJIIg temperature conditions. 1 i

In testimonywhereof we aflix our signatures.

CHARLES A. HANSER. ERWIN A. LOCKWOOD.

